PROJECT SUMMARY Heat shock protein 90 (Hsp90) and Hsp70 are molecular chaperones that facilitate protein folding, maturation and clearance. It is well recognized that targeting Hsp90 and Hsp70 with small molecule drugs may improve proteostatic neurodegenerative diseases by enhancing the clearance of neurotoxic protein aggregates. However, we have identified that pharmacologically targeting molecular chaperones has therapeutic value in treating peripheral neuropathies whose etiology is independent of proteostasis. The traditional small molecule approach for targeting Hsp90 has relied on drugs that inhibit its N-terminal ATPase activity. Lamentably, the translational success of these drugs has been hindered by the complex chemical biology of targeting the Hsp90 N-terminal ATP binding site. In contrast, we have developed ?novologues? as small molecule inhibitors of the Hsp90 C-terminal domain that circumvent limitations that have confounded the clinical prospects of Hsp90 as a therapeutic target. Novologues are orally bioavailable and non-toxic molecules that promote a cytoprotective response that constitutes a paradigm shift for the treatment of diabetic peripheral neuropathy (DPN) and potentially, demyelinating neuropathies (DymN). Our published and unpublished data support that novologues improve physiologic measures of DPN and DymN in an Hsp70- dependent manner by improving mitochondrial bioenergetics in DPN and inhibiting the induction of c-jun, a negative regulator of myelination, that contributes to DymN. Thus, our central hypothesis is that modulating the activity of molecular chaperones with novologues will provide an innovative and novel approach for the treatment of both DPN and some forms of DymN. Our efforts over the four years of NIH funding have led to the licensing of our lead novologue, KU-596, to a pharmaceutical company and its advancement to Phase I studies for treating DPN. To build upon this success, we have identified attributes and detriments of KU- 596. Specific Aim 1 focuses on the rationale design and development of ?noviomimetics? as a new class of molecules that will improve on the chemical biology of novologues by increasing potency, requiring fewer synthetic steps and exhibiting better metabolic stability. Specific Aim 2 will use two cell-based screening assays to examine the ability to improve mitochondrial bioenergetics in diabetic sensory neurons or increase the degradation of the transcription factor, c-jun. Importantly, we provide evidence that these biochemical readouts are prognostic for in vivo efficacy to improve DPN and DymN, respectively. Compounds that advance through the cell-based assay will undergo ADME screening to aid selecting candidates for in vivo testing in a mouse model of DPN and two models that recapitulate a human demyelinating motor neuropathy. The outcome of this work will extend the success of our drug development program and identify noviomimetics as a new class of neuroprotective compounds for treating peripheral neuropathies.